Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 1611 insertions, 0 deletions

diff --git a/drivers/usb/host/xen-hcd.c b/drivers/usb/host/xen-hcd.c
new file mode 100644
index 000000000..0a94d3029
--- /dev/null
+++ b/drivers/usb/host/xen-hcd.c
@@ -0,0 +1,1611 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * xen-hcd.c
+ *
+ * Xen USB Virtual Host Controller driver
+ *
+ * Copyright (C) 2009, FUJITSU LABORATORIES LTD.
+ * Author: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
+ */
+
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/list.h>
+#include <linux/usb/hcd.h>
+#include <linux/io.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/page.h>
+
+#include <xen/interface/io/usbif.h>
+
+/* Private per-URB data */
+struct urb_priv {
+	struct list_head list;
+	struct urb *urb;
+	int req_id;		/* RING_REQUEST id for submitting */
+	int unlink_req_id;	/* RING_REQUEST id for unlinking */
+	int status;
+	bool unlinked;		/* dequeued marker */
+};
+
+/* virtual roothub port status */
+struct rhport_status {
+	__u32 status;
+	bool resuming;		/* in resuming */
+	bool c_connection;	/* connection changed */
+	unsigned long timeout;
+};
+
+/* status of attached device */
+struct vdevice_status {
+	int devnum;
+	enum usb_device_state status;
+	enum usb_device_speed speed;
+};
+
+/* RING request shadow */
+struct usb_shadow {
+	struct xenusb_urb_request req;
+	struct urb *urb;
+	bool in_flight;
+};
+
+struct xenhcd_info {
+	/* Virtual Host Controller has 4 urb queues */
+	struct list_head pending_submit_list;
+	struct list_head pending_unlink_list;
+	struct list_head in_progress_list;
+	struct list_head giveback_waiting_list;
+
+	spinlock_t lock;
+
+	/* timer that kick pending and giveback waiting urbs */
+	struct timer_list watchdog;
+	unsigned long actions;
+
+	/* virtual root hub */
+	int rh_numports;
+	struct rhport_status ports[XENUSB_MAX_PORTNR];
+	struct vdevice_status devices[XENUSB_MAX_PORTNR];
+
+	/* Xen related staff */
+	struct xenbus_device *xbdev;
+	int urb_ring_ref;
+	int conn_ring_ref;
+	struct xenusb_urb_front_ring urb_ring;
+	struct xenusb_conn_front_ring conn_ring;
+
+	unsigned int evtchn;
+	unsigned int irq;
+	struct usb_shadow shadow[XENUSB_URB_RING_SIZE];
+	unsigned int shadow_free;
+
+	bool error;
+};
+
+#define XENHCD_RING_JIFFIES (HZ/200)
+#define XENHCD_SCAN_JIFFIES 1
+
+enum xenhcd_timer_action {
+	TIMER_RING_WATCHDOG,
+	TIMER_SCAN_PENDING_URBS,
+};
+
+static struct kmem_cache *xenhcd_urbp_cachep;
+
+static inline struct xenhcd_info *xenhcd_hcd_to_info(struct usb_hcd *hcd)
+{
+	return (struct xenhcd_info *)hcd->hcd_priv;
+}
+
+static inline struct usb_hcd *xenhcd_info_to_hcd(struct xenhcd_info *info)
+{
+	return container_of((void *)info, struct usb_hcd, hcd_priv);
+}
+
+static void xenhcd_set_error(struct xenhcd_info *info, const char *msg)
+{
+	info->error = true;
+
+	pr_alert("xen-hcd: protocol error: %s!\n", msg);
+}
+
+static inline void xenhcd_timer_action_done(struct xenhcd_info *info,
+					    enum xenhcd_timer_action action)
+{
+	clear_bit(action, &info->actions);
+}
+
+static void xenhcd_timer_action(struct xenhcd_info *info,
+				enum xenhcd_timer_action action)
+{
+	if (timer_pending(&info->watchdog) &&
+	    test_bit(TIMER_SCAN_PENDING_URBS, &info->actions))
+		return;
+
+	if (!test_and_set_bit(action, &info->actions)) {
+		unsigned long t;
+
+		switch (action) {
+		case TIMER_RING_WATCHDOG:
+			t = XENHCD_RING_JIFFIES;
+			break;
+		default:
+			t = XENHCD_SCAN_JIFFIES;
+			break;
+		}
+		mod_timer(&info->watchdog, t + jiffies);
+	}
+}
+
+/*
+ * set virtual port connection status
+ */
+static void xenhcd_set_connect_state(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	if (info->ports[port].status & USB_PORT_STAT_POWER) {
+		switch (info->devices[port].speed) {
+		case XENUSB_SPEED_NONE:
+			info->ports[port].status &=
+				~(USB_PORT_STAT_CONNECTION |
+				  USB_PORT_STAT_ENABLE |
+				  USB_PORT_STAT_LOW_SPEED |
+				  USB_PORT_STAT_HIGH_SPEED |
+				  USB_PORT_STAT_SUSPEND);
+			break;
+		case XENUSB_SPEED_LOW:
+			info->ports[port].status |= USB_PORT_STAT_CONNECTION;
+			info->ports[port].status |= USB_PORT_STAT_LOW_SPEED;
+			break;
+		case XENUSB_SPEED_FULL:
+			info->ports[port].status |= USB_PORT_STAT_CONNECTION;
+			break;
+		case XENUSB_SPEED_HIGH:
+			info->ports[port].status |= USB_PORT_STAT_CONNECTION;
+			info->ports[port].status |= USB_PORT_STAT_HIGH_SPEED;
+			break;
+		default: /* error */
+			return;
+		}
+		info->ports[port].status |= (USB_PORT_STAT_C_CONNECTION << 16);
+	}
+}
+
+/*
+ * set virtual device connection status
+ */
+static int xenhcd_rhport_connect(struct xenhcd_info *info, __u8 portnum,
+				 __u8 speed)
+{
+	int port;
+
+	if (portnum < 1 || portnum > info->rh_numports)
+		return -EINVAL; /* invalid port number */
+
+	port = portnum - 1;
+	if (info->devices[port].speed != speed) {
+		switch (speed) {
+		case XENUSB_SPEED_NONE: /* disconnect */
+			info->devices[port].status = USB_STATE_NOTATTACHED;
+			break;
+		case XENUSB_SPEED_LOW:
+		case XENUSB_SPEED_FULL:
+		case XENUSB_SPEED_HIGH:
+			info->devices[port].status = USB_STATE_ATTACHED;
+			break;
+		default: /* error */
+			return -EINVAL;
+		}
+		info->devices[port].speed = speed;
+		info->ports[port].c_connection = true;
+
+		xenhcd_set_connect_state(info, portnum);
+	}
+
+	return 0;
+}
+
+/*
+ * SetPortFeature(PORT_SUSPENDED)
+ */
+static void xenhcd_rhport_suspend(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	info->ports[port].status |= USB_PORT_STAT_SUSPEND;
+	info->devices[port].status = USB_STATE_SUSPENDED;
+}
+
+/*
+ * ClearPortFeature(PORT_SUSPENDED)
+ */
+static void xenhcd_rhport_resume(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	if (info->ports[port].status & USB_PORT_STAT_SUSPEND) {
+		info->ports[port].resuming = true;
+		info->ports[port].timeout = jiffies + msecs_to_jiffies(20);
+	}
+}
+
+/*
+ * SetPortFeature(PORT_POWER)
+ */
+static void xenhcd_rhport_power_on(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	if ((info->ports[port].status & USB_PORT_STAT_POWER) == 0) {
+		info->ports[port].status |= USB_PORT_STAT_POWER;
+		if (info->devices[port].status != USB_STATE_NOTATTACHED)
+			info->devices[port].status = USB_STATE_POWERED;
+		if (info->ports[port].c_connection)
+			xenhcd_set_connect_state(info, portnum);
+	}
+}
+
+/*
+ * ClearPortFeature(PORT_POWER)
+ * SetConfiguration(non-zero)
+ * Power_Source_Off
+ * Over-current
+ */
+static void xenhcd_rhport_power_off(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	if (info->ports[port].status & USB_PORT_STAT_POWER) {
+		info->ports[port].status = 0;
+		if (info->devices[port].status != USB_STATE_NOTATTACHED)
+			info->devices[port].status = USB_STATE_ATTACHED;
+	}
+}
+
+/*
+ * ClearPortFeature(PORT_ENABLE)
+ */
+static void xenhcd_rhport_disable(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	info->ports[port].status &= ~USB_PORT_STAT_ENABLE;
+	info->ports[port].status &= ~USB_PORT_STAT_SUSPEND;
+	info->ports[port].resuming = false;
+	if (info->devices[port].status != USB_STATE_NOTATTACHED)
+		info->devices[port].status = USB_STATE_POWERED;
+}
+
+/*
+ * SetPortFeature(PORT_RESET)
+ */
+static void xenhcd_rhport_reset(struct xenhcd_info *info, int portnum)
+{
+	int port;
+
+	port = portnum - 1;
+	info->ports[port].status &= ~(USB_PORT_STAT_ENABLE |
+				      USB_PORT_STAT_LOW_SPEED |
+				      USB_PORT_STAT_HIGH_SPEED);
+	info->ports[port].status |= USB_PORT_STAT_RESET;
+
+	if (info->devices[port].status != USB_STATE_NOTATTACHED)
+		info->devices[port].status = USB_STATE_ATTACHED;
+
+	/* 10msec reset signaling */
+	info->ports[port].timeout = jiffies + msecs_to_jiffies(10);
+}
+
+#ifdef CONFIG_PM
+static int xenhcd_bus_suspend(struct usb_hcd *hcd)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+	int ret = 0;
+	int i, ports;
+
+	ports = info->rh_numports;
+
+	spin_lock_irq(&info->lock);
+	if (!test_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags)) {
+		ret = -ESHUTDOWN;
+	} else {
+		/* suspend any active ports*/
+		for (i = 1; i <= ports; i++)
+			xenhcd_rhport_suspend(info, i);
+	}
+	spin_unlock_irq(&info->lock);
+
+	timer_delete_sync(&info->watchdog);
+
+	return ret;
+}
+
+static int xenhcd_bus_resume(struct usb_hcd *hcd)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+	int ret = 0;
+	int i, ports;
+
+	ports = info->rh_numports;
+
+	spin_lock_irq(&info->lock);
+	if (!test_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags)) {
+		ret = -ESHUTDOWN;
+	} else {
+		/* resume any suspended ports*/
+		for (i = 1; i <= ports; i++)
+			xenhcd_rhport_resume(info, i);
+	}
+	spin_unlock_irq(&info->lock);
+
+	return ret;
+}
+#endif
+
+static void xenhcd_hub_descriptor(struct xenhcd_info *info,
+				  struct usb_hub_descriptor *desc)
+{
+	__u16 temp;
+	int ports = info->rh_numports;
+
+	desc->bDescriptorType = 0x29;
+	desc->bPwrOn2PwrGood = 10; /* EHCI says 20ms max */
+	desc->bHubContrCurrent = 0;
+	desc->bNbrPorts = ports;
+
+	/* size of DeviceRemovable and PortPwrCtrlMask fields */
+	temp = 1 + (ports / 8);
+	desc->bDescLength = 7 + 2 * temp;
+
+	/* bitmaps for DeviceRemovable and PortPwrCtrlMask */
+	memset(&desc->u.hs.DeviceRemovable[0], 0, temp);
+	memset(&desc->u.hs.DeviceRemovable[temp], 0xff, temp);
+
+	/* per-port over current reporting and no power switching */
+	temp = 0x000a;
+	desc->wHubCharacteristics = cpu_to_le16(temp);
+}
+
+/* port status change mask for hub_status_data */
+#define PORT_C_MASK	((USB_PORT_STAT_C_CONNECTION |		\
+			  USB_PORT_STAT_C_ENABLE |		\
+			  USB_PORT_STAT_C_SUSPEND |		\
+			  USB_PORT_STAT_C_OVERCURRENT |		\
+			  USB_PORT_STAT_C_RESET) << 16)
+
+/*
+ * See USB 2.0 Spec, 11.12.4 Hub and Port Status Change Bitmap.
+ * If port status changed, writes the bitmap to buf and return
+ * that length(number of bytes).
+ * If Nothing changed, return 0.
+ */
+static int xenhcd_hub_status_data(struct usb_hcd *hcd, char *buf)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+	int ports;
+	int i;
+	unsigned long flags;
+	int ret;
+	int changed = 0;
+
+	/* initialize the status to no-changes */
+	ports = info->rh_numports;
+	ret = 1 + (ports / 8);
+	memset(buf, 0, ret);
+
+	spin_lock_irqsave(&info->lock, flags);
+
+	for (i = 0; i < ports; i++) {
+		/* check status for each port */
+		if (info->ports[i].status & PORT_C_MASK) {
+			buf[(i + 1) / 8] |= 1 << (i + 1) % 8;
+			changed = 1;
+		}
+	}
+
+	if ((hcd->state == HC_STATE_SUSPENDED) && (changed == 1))
+		usb_hcd_resume_root_hub(hcd);
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return changed ? ret : 0;
+}
+
+static int xenhcd_hub_control(struct usb_hcd *hcd, __u16 typeReq, __u16 wValue,
+			      __u16 wIndex, char *buf, __u16 wLength)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+	int ports = info->rh_numports;
+	unsigned long flags;
+	int ret = 0;
+	int i;
+	int changed = 0;
+
+	spin_lock_irqsave(&info->lock, flags);
+	switch (typeReq) {
+	case ClearHubFeature:
+		/* ignore this request */
+		break;
+	case ClearPortFeature:
+		if (!wIndex || wIndex > ports)
+			goto error;
+
+		switch (wValue) {
+		case USB_PORT_FEAT_SUSPEND:
+			xenhcd_rhport_resume(info, wIndex);
+			break;
+		case USB_PORT_FEAT_POWER:
+			xenhcd_rhport_power_off(info, wIndex);
+			break;
+		case USB_PORT_FEAT_ENABLE:
+			xenhcd_rhport_disable(info, wIndex);
+			break;
+		case USB_PORT_FEAT_C_CONNECTION:
+			info->ports[wIndex - 1].c_connection = false;
+			fallthrough;
+		default:
+			info->ports[wIndex - 1].status &= ~(1 << wValue);
+			break;
+		}
+		break;
+	case GetHubDescriptor:
+		xenhcd_hub_descriptor(info, (struct usb_hub_descriptor *)buf);
+		break;
+	case GetHubStatus:
+		/* always local power supply good and no over-current exists. */
+		*(__le32 *)buf = cpu_to_le32(0);
+		break;
+	case GetPortStatus:
+		if (!wIndex || wIndex > ports)
+			goto error;
+
+		wIndex--;
+
+		/* resume completion */
+		if (info->ports[wIndex].resuming &&
+		    time_after_eq(jiffies, info->ports[wIndex].timeout)) {
+			info->ports[wIndex].status |=
+				USB_PORT_STAT_C_SUSPEND << 16;
+			info->ports[wIndex].status &= ~USB_PORT_STAT_SUSPEND;
+		}
+
+		/* reset completion */
+		if ((info->ports[wIndex].status & USB_PORT_STAT_RESET) != 0 &&
+		    time_after_eq(jiffies, info->ports[wIndex].timeout)) {
+			info->ports[wIndex].status |=
+				USB_PORT_STAT_C_RESET << 16;
+			info->ports[wIndex].status &= ~USB_PORT_STAT_RESET;
+
+			if (info->devices[wIndex].status !=
+			    USB_STATE_NOTATTACHED) {
+				info->ports[wIndex].status |=
+					USB_PORT_STAT_ENABLE;
+				info->devices[wIndex].status =
+					USB_STATE_DEFAULT;
+			}
+
+			switch (info->devices[wIndex].speed) {
+			case XENUSB_SPEED_LOW:
+				info->ports[wIndex].status |=
+					USB_PORT_STAT_LOW_SPEED;
+				break;
+			case XENUSB_SPEED_HIGH:
+				info->ports[wIndex].status |=
+					USB_PORT_STAT_HIGH_SPEED;
+				break;
+			default:
+				break;
+			}
+		}
+
+		*(__le32 *)buf = cpu_to_le32(info->ports[wIndex].status);
+		break;
+	case SetPortFeature:
+		if (!wIndex || wIndex > ports)
+			goto error;
+
+		switch (wValue) {
+		case USB_PORT_FEAT_POWER:
+			xenhcd_rhport_power_on(info, wIndex);
+			break;
+		case USB_PORT_FEAT_RESET:
+			xenhcd_rhport_reset(info, wIndex);
+			break;
+		case USB_PORT_FEAT_SUSPEND:
+			xenhcd_rhport_suspend(info, wIndex);
+			break;
+		default:
+			if (info->ports[wIndex-1].status & USB_PORT_STAT_POWER)
+				info->ports[wIndex-1].status |= (1 << wValue);
+		}
+		break;
+
+	case SetHubFeature:
+		/* not supported */
+	default:
+error:
+		ret = -EPIPE;
+	}
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	/* check status for each port */
+	for (i = 0; i < ports; i++) {
+		if (info->ports[i].status & PORT_C_MASK)
+			changed = 1;
+	}
+	if (changed)
+		usb_hcd_poll_rh_status(hcd);
+
+	return ret;
+}
+
+static void xenhcd_free_urb_priv(struct urb_priv *urbp)
+{
+	urbp->urb->hcpriv = NULL;
+	kmem_cache_free(xenhcd_urbp_cachep, urbp);
+}
+
+static inline unsigned int xenhcd_get_id_from_freelist(struct xenhcd_info *info)
+{
+	unsigned int free;
+
+	free = info->shadow_free;
+	info->shadow_free = info->shadow[free].req.id;
+	info->shadow[free].req.id = 0x0fff; /* debug */
+	return free;
+}
+
+static inline void xenhcd_add_id_to_freelist(struct xenhcd_info *info,
+					     unsigned int id)
+{
+	info->shadow[id].req.id	= info->shadow_free;
+	info->shadow[id].urb = NULL;
+	info->shadow_free = id;
+}
+
+static inline int xenhcd_count_pages(void *addr, int length)
+{
+	unsigned long vaddr = (unsigned long)addr;
+
+	return PFN_UP(vaddr + length) - PFN_DOWN(vaddr);
+}
+
+static void xenhcd_gnttab_map(struct xenhcd_info *info, void *addr, int length,
+			      grant_ref_t *gref_head,
+			      struct xenusb_request_segment *seg,
+			      int nr_pages, int flags)
+{
+	grant_ref_t ref;
+	unsigned int offset;
+	unsigned int len = length;
+	unsigned int bytes;
+	int i;
+
+	for (i = 0; i < nr_pages; i++) {
+		offset = offset_in_page(addr);
+
+		bytes = PAGE_SIZE - offset;
+		if (bytes > len)
+			bytes = len;
+
+		ref = gnttab_claim_grant_reference(gref_head);
+		gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
+						virt_to_gfn(addr), flags);
+		seg[i].gref = ref;
+		seg[i].offset = (__u16)offset;
+		seg[i].length = (__u16)bytes;
+
+		addr += bytes;
+		len -= bytes;
+	}
+}
+
+static __u32 xenhcd_pipe_urb_to_xenusb(__u32 urb_pipe, __u8 port)
+{
+	static __u32 pipe;
+
+	pipe = usb_pipedevice(urb_pipe) << XENUSB_PIPE_DEV_SHIFT;
+	pipe |= usb_pipeendpoint(urb_pipe) << XENUSB_PIPE_EP_SHIFT;
+	if (usb_pipein(urb_pipe))
+		pipe |= XENUSB_PIPE_DIR;
+	switch (usb_pipetype(urb_pipe)) {
+	case PIPE_ISOCHRONOUS:
+		pipe |= XENUSB_PIPE_TYPE_ISOC << XENUSB_PIPE_TYPE_SHIFT;
+		break;
+	case PIPE_INTERRUPT:
+		pipe |= XENUSB_PIPE_TYPE_INT << XENUSB_PIPE_TYPE_SHIFT;
+		break;
+	case PIPE_CONTROL:
+		pipe |= XENUSB_PIPE_TYPE_CTRL << XENUSB_PIPE_TYPE_SHIFT;
+		break;
+	case PIPE_BULK:
+		pipe |= XENUSB_PIPE_TYPE_BULK << XENUSB_PIPE_TYPE_SHIFT;
+		break;
+	}
+	pipe = xenusb_setportnum_pipe(pipe, port);
+
+	return pipe;
+}
+
+static int xenhcd_map_urb_for_request(struct xenhcd_info *info, struct urb *urb,
+				      struct xenusb_urb_request *req)
+{
+	grant_ref_t gref_head;
+	int nr_buff_pages = 0;
+	int nr_isodesc_pages = 0;
+	int nr_grants = 0;
+
+	if (urb->transfer_buffer_length) {
+		nr_buff_pages = xenhcd_count_pages(urb->transfer_buffer,
+						urb->transfer_buffer_length);
+
+		if (usb_pipeisoc(urb->pipe))
+			nr_isodesc_pages = xenhcd_count_pages(
+				&urb->iso_frame_desc[0],
+				sizeof(struct usb_iso_packet_descriptor) *
+				urb->number_of_packets);
+
+		nr_grants = nr_buff_pages + nr_isodesc_pages;
+		if (nr_grants > XENUSB_MAX_SEGMENTS_PER_REQUEST) {
+			pr_err("xenhcd: error: %d grants\n", nr_grants);
+			return -E2BIG;
+		}
+
+		if (gnttab_alloc_grant_references(nr_grants, &gref_head)) {
+			pr_err("xenhcd: gnttab_alloc_grant_references() error\n");
+			return -ENOMEM;
+		}
+
+		xenhcd_gnttab_map(info, urb->transfer_buffer,
+				  urb->transfer_buffer_length, &gref_head,
+				  &req->seg[0], nr_buff_pages,
+				  usb_pipein(urb->pipe) ? 0 : GTF_readonly);
+	}
+
+	req->pipe = xenhcd_pipe_urb_to_xenusb(urb->pipe, urb->dev->portnum);
+	req->transfer_flags = 0;
+	if (urb->transfer_flags & URB_SHORT_NOT_OK)
+		req->transfer_flags |= XENUSB_SHORT_NOT_OK;
+	req->buffer_length = urb->transfer_buffer_length;
+	req->nr_buffer_segs = nr_buff_pages;
+
+	switch (usb_pipetype(urb->pipe)) {
+	case PIPE_ISOCHRONOUS:
+		req->u.isoc.interval = urb->interval;
+		req->u.isoc.start_frame = urb->start_frame;
+		req->u.isoc.number_of_packets = urb->number_of_packets;
+		req->u.isoc.nr_frame_desc_segs = nr_isodesc_pages;
+
+		xenhcd_gnttab_map(info, &urb->iso_frame_desc[0],
+				  sizeof(struct usb_iso_packet_descriptor) *
+				  urb->number_of_packets,
+				  &gref_head, &req->seg[nr_buff_pages],
+				  nr_isodesc_pages, 0);
+		break;
+	case PIPE_INTERRUPT:
+		req->u.intr.interval = urb->interval;
+		break;
+	case PIPE_CONTROL:
+		if (urb->setup_packet)
+			memcpy(req->u.ctrl, urb->setup_packet, 8);
+		break;
+	case PIPE_BULK:
+		break;
+	default:
+		break;
+	}
+
+	if (nr_grants)
+		gnttab_free_grant_references(gref_head);
+
+	return 0;
+}
+
+static void xenhcd_gnttab_done(struct xenhcd_info *info, unsigned int id)
+{
+	struct usb_shadow *shadow = info->shadow + id;
+	int nr_segs = 0;
+	int i;
+
+	if (!shadow->in_flight) {
+		xenhcd_set_error(info, "Illegal request id");
+		return;
+	}
+	shadow->in_flight = false;
+
+	nr_segs = shadow->req.nr_buffer_segs;
+
+	if (xenusb_pipeisoc(shadow->req.pipe))
+		nr_segs += shadow->req.u.isoc.nr_frame_desc_segs;
+
+	for (i = 0; i < nr_segs; i++) {
+		if (!gnttab_try_end_foreign_access(shadow->req.seg[i].gref))
+			xenhcd_set_error(info, "backend didn't release grant");
+	}
+
+	shadow->req.nr_buffer_segs = 0;
+	shadow->req.u.isoc.nr_frame_desc_segs = 0;
+}
+
+static int xenhcd_translate_status(int status)
+{
+	switch (status) {
+	case XENUSB_STATUS_OK:
+		return 0;
+	case XENUSB_STATUS_NODEV:
+		return -ENODEV;
+	case XENUSB_STATUS_INVAL:
+		return -EINVAL;
+	case XENUSB_STATUS_STALL:
+		return -EPIPE;
+	case XENUSB_STATUS_IOERROR:
+		return -EPROTO;
+	case XENUSB_STATUS_BABBLE:
+		return -EOVERFLOW;
+	default:
+		return -ESHUTDOWN;
+	}
+}
+
+static void xenhcd_giveback_urb(struct xenhcd_info *info, struct urb *urb,
+				int status)
+{
+	struct urb_priv *urbp = (struct urb_priv *)urb->hcpriv;
+	int priv_status = urbp->status;
+
+	list_del_init(&urbp->list);
+	xenhcd_free_urb_priv(urbp);
+
+	if (urb->status == -EINPROGRESS)
+		urb->status = xenhcd_translate_status(status);
+
+	spin_unlock(&info->lock);
+	usb_hcd_giveback_urb(xenhcd_info_to_hcd(info), urb,
+			     priv_status <= 0 ? priv_status : urb->status);
+	spin_lock(&info->lock);
+}
+
+static int xenhcd_do_request(struct xenhcd_info *info, struct urb_priv *urbp)
+{
+	struct xenusb_urb_request *req;
+	struct urb *urb = urbp->urb;
+	unsigned int id;
+	int notify;
+	int ret;
+
+	id = xenhcd_get_id_from_freelist(info);
+	req = &info->shadow[id].req;
+	req->id = id;
+
+	if (unlikely(urbp->unlinked)) {
+		req->u.unlink.unlink_id = urbp->req_id;
+		req->pipe = xenusb_setunlink_pipe(xenhcd_pipe_urb_to_xenusb(
+						 urb->pipe, urb->dev->portnum));
+		urbp->unlink_req_id = id;
+	} else {
+		ret = xenhcd_map_urb_for_request(info, urb, req);
+		if (ret) {
+			xenhcd_add_id_to_freelist(info, id);
+			return ret;
+		}
+		urbp->req_id = id;
+	}
+
+	req = RING_GET_REQUEST(&info->urb_ring, info->urb_ring.req_prod_pvt);
+	*req = info->shadow[id].req;
+
+	info->urb_ring.req_prod_pvt++;
+	info->shadow[id].urb = urb;
+	info->shadow[id].in_flight = true;
+
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->urb_ring, notify);
+	if (notify)
+		notify_remote_via_irq(info->irq);
+
+	return 0;
+}
+
+static void xenhcd_kick_pending_urbs(struct xenhcd_info *info)
+{
+	struct urb_priv *urbp;
+
+	while (!list_empty(&info->pending_submit_list)) {
+		if (RING_FULL(&info->urb_ring)) {
+			xenhcd_timer_action(info, TIMER_RING_WATCHDOG);
+			return;
+		}
+
+		urbp = list_entry(info->pending_submit_list.next,
+				  struct urb_priv, list);
+		if (!xenhcd_do_request(info, urbp))
+			list_move_tail(&urbp->list, &info->in_progress_list);
+		else
+			xenhcd_giveback_urb(info, urbp->urb, -ESHUTDOWN);
+	}
+	xenhcd_timer_action_done(info, TIMER_SCAN_PENDING_URBS);
+}
+
+/*
+ * caller must lock info->lock
+ */
+static void xenhcd_cancel_all_enqueued_urbs(struct xenhcd_info *info)
+{
+	struct urb_priv *urbp, *tmp;
+	int req_id;
+
+	list_for_each_entry_safe(urbp, tmp, &info->in_progress_list, list) {
+		req_id = urbp->req_id;
+		if (!urbp->unlinked) {
+			xenhcd_gnttab_done(info, req_id);
+			if (info->error)
+				return;
+			if (urbp->urb->status == -EINPROGRESS)
+				/* not dequeued */
+				xenhcd_giveback_urb(info, urbp->urb,
+						    -ESHUTDOWN);
+			else	/* dequeued */
+				xenhcd_giveback_urb(info, urbp->urb,
+						    urbp->urb->status);
+		}
+		info->shadow[req_id].urb = NULL;
+	}
+
+	list_for_each_entry_safe(urbp, tmp, &info->pending_submit_list, list)
+		xenhcd_giveback_urb(info, urbp->urb, -ESHUTDOWN);
+}
+
+/*
+ * caller must lock info->lock
+ */
+static void xenhcd_giveback_unlinked_urbs(struct xenhcd_info *info)
+{
+	struct urb_priv *urbp, *tmp;
+
+	list_for_each_entry_safe(urbp, tmp, &info->giveback_waiting_list, list)
+		xenhcd_giveback_urb(info, urbp->urb, urbp->urb->status);
+}
+
+static int xenhcd_submit_urb(struct xenhcd_info *info, struct urb_priv *urbp)
+{
+	int ret;
+
+	if (RING_FULL(&info->urb_ring)) {
+		list_add_tail(&urbp->list, &info->pending_submit_list);
+		xenhcd_timer_action(info, TIMER_RING_WATCHDOG);
+		return 0;
+	}
+
+	if (!list_empty(&info->pending_submit_list)) {
+		list_add_tail(&urbp->list, &info->pending_submit_list);
+		xenhcd_timer_action(info, TIMER_SCAN_PENDING_URBS);
+		return 0;
+	}
+
+	ret = xenhcd_do_request(info, urbp);
+	if (ret == 0)
+		list_add_tail(&urbp->list, &info->in_progress_list);
+
+	return ret;
+}
+
+static int xenhcd_unlink_urb(struct xenhcd_info *info, struct urb_priv *urbp)
+{
+	int ret;
+
+	/* already unlinked? */
+	if (urbp->unlinked)
+		return -EBUSY;
+
+	urbp->unlinked = true;
+
+	/* the urb is still in pending_submit queue */
+	if (urbp->req_id == ~0) {
+		list_move_tail(&urbp->list, &info->giveback_waiting_list);
+		xenhcd_timer_action(info, TIMER_SCAN_PENDING_URBS);
+		return 0;
+	}
+
+	/* send unlink request to backend */
+	if (RING_FULL(&info->urb_ring)) {
+		list_move_tail(&urbp->list, &info->pending_unlink_list);
+		xenhcd_timer_action(info, TIMER_RING_WATCHDOG);
+		return 0;
+	}
+
+	if (!list_empty(&info->pending_unlink_list)) {
+		list_move_tail(&urbp->list, &info->pending_unlink_list);
+		xenhcd_timer_action(info, TIMER_SCAN_PENDING_URBS);
+		return 0;
+	}
+
+	ret = xenhcd_do_request(info, urbp);
+	if (ret == 0)
+		list_move_tail(&urbp->list, &info->in_progress_list);
+
+	return ret;
+}
+
+static void xenhcd_res_to_urb(struct xenhcd_info *info,
+			      struct xenusb_urb_response *res, struct urb *urb)
+{
+	if (unlikely(!urb))
+		return;
+
+	if (res->actual_length > urb->transfer_buffer_length)
+		urb->actual_length = urb->transfer_buffer_length;
+	else if (res->actual_length < 0)
+		urb->actual_length = 0;
+	else
+		urb->actual_length = res->actual_length;
+	urb->error_count = res->error_count;
+	urb->start_frame = res->start_frame;
+	xenhcd_giveback_urb(info, urb, res->status);
+}
+
+static int xenhcd_urb_request_done(struct xenhcd_info *info,
+				   unsigned int *eoiflag)
+{
+	struct xenusb_urb_response res;
+	RING_IDX i, rp;
+	__u16 id;
+	int more_to_do = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->lock, flags);
+
+	rp = info->urb_ring.sring->rsp_prod;
+	if (RING_RESPONSE_PROD_OVERFLOW(&info->urb_ring, rp)) {
+		xenhcd_set_error(info, "Illegal index on urb-ring");
+		goto err;
+	}
+	rmb(); /* ensure we see queued responses up to "rp" */
+
+	for (i = info->urb_ring.rsp_cons; i != rp; i++) {
+		RING_COPY_RESPONSE(&info->urb_ring, i, &res);
+		id = res.id;
+		if (id >= XENUSB_URB_RING_SIZE) {
+			xenhcd_set_error(info, "Illegal data on urb-ring");
+			goto err;
+		}
+
+		if (likely(xenusb_pipesubmit(info->shadow[id].req.pipe))) {
+			xenhcd_gnttab_done(info, id);
+			if (info->error)
+				goto err;
+			xenhcd_res_to_urb(info, &res, info->shadow[id].urb);
+		}
+
+		xenhcd_add_id_to_freelist(info, id);
+
+		*eoiflag = 0;
+	}
+	info->urb_ring.rsp_cons = i;
+
+	if (i != info->urb_ring.req_prod_pvt)
+		RING_FINAL_CHECK_FOR_RESPONSES(&info->urb_ring, more_to_do);
+	else
+		info->urb_ring.sring->rsp_event = i + 1;
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return more_to_do;
+
+ err:
+	spin_unlock_irqrestore(&info->lock, flags);
+	return 0;
+}
+
+static int xenhcd_conn_notify(struct xenhcd_info *info, unsigned int *eoiflag)
+{
+	struct xenusb_conn_response res;
+	struct xenusb_conn_request *req;
+	RING_IDX rc, rp;
+	__u16 id;
+	__u8 portnum, speed;
+	int more_to_do = 0;
+	int notify;
+	int port_changed = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->lock, flags);
+
+	rc = info->conn_ring.rsp_cons;
+	rp = info->conn_ring.sring->rsp_prod;
+	if (RING_RESPONSE_PROD_OVERFLOW(&info->conn_ring, rp)) {
+		xenhcd_set_error(info, "Illegal index on conn-ring");
+		spin_unlock_irqrestore(&info->lock, flags);
+		return 0;
+	}
+	rmb(); /* ensure we see queued responses up to "rp" */
+
+	while (rc != rp) {
+		RING_COPY_RESPONSE(&info->conn_ring, rc, &res);
+		id = res.id;
+		portnum = res.portnum;
+		speed = res.speed;
+		info->conn_ring.rsp_cons = ++rc;
+
+		if (xenhcd_rhport_connect(info, portnum, speed)) {
+			xenhcd_set_error(info, "Illegal data on conn-ring");
+			spin_unlock_irqrestore(&info->lock, flags);
+			return 0;
+		}
+
+		if (info->ports[portnum - 1].c_connection)
+			port_changed = 1;
+
+		barrier();
+
+		req = RING_GET_REQUEST(&info->conn_ring,
+				       info->conn_ring.req_prod_pvt);
+		req->id = id;
+		info->conn_ring.req_prod_pvt++;
+
+		*eoiflag = 0;
+	}
+
+	if (rc != info->conn_ring.req_prod_pvt)
+		RING_FINAL_CHECK_FOR_RESPONSES(&info->conn_ring, more_to_do);
+	else
+		info->conn_ring.sring->rsp_event = rc + 1;
+
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->conn_ring, notify);
+	if (notify)
+		notify_remote_via_irq(info->irq);
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	if (port_changed)
+		usb_hcd_poll_rh_status(xenhcd_info_to_hcd(info));
+
+	return more_to_do;
+}
+
+static irqreturn_t xenhcd_int(int irq, void *dev_id)
+{
+	struct xenhcd_info *info = (struct xenhcd_info *)dev_id;
+	unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS;
+
+	if (unlikely(info->error)) {
+		xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS);
+		return IRQ_HANDLED;
+	}
+
+	while (xenhcd_urb_request_done(info, &eoiflag) |
+	       xenhcd_conn_notify(info, &eoiflag))
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+
+	xen_irq_lateeoi(irq, eoiflag);
+	return IRQ_HANDLED;
+}
+
+static void xenhcd_destroy_rings(struct xenhcd_info *info)
+{
+	if (info->irq)
+		unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+
+	xenbus_teardown_ring((void **)&info->urb_ring.sring, 1,
+			     &info->urb_ring_ref);
+	xenbus_teardown_ring((void **)&info->conn_ring.sring, 1,
+			     &info->conn_ring_ref);
+}
+
+static int xenhcd_setup_rings(struct xenbus_device *dev,
+			      struct xenhcd_info *info)
+{
+	struct xenusb_urb_sring *urb_sring;
+	struct xenusb_conn_sring *conn_sring;
+	int err;
+
+	info->conn_ring_ref = INVALID_GRANT_REF;
+	err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH,
+				(void **)&urb_sring, 1, &info->urb_ring_ref);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "allocating urb ring");
+		return err;
+	}
+	XEN_FRONT_RING_INIT(&info->urb_ring, urb_sring, PAGE_SIZE);
+
+	err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH,
+				(void **)&conn_sring, 1, &info->conn_ring_ref);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "allocating conn ring");
+		goto fail;
+	}
+	XEN_FRONT_RING_INIT(&info->conn_ring, conn_sring, PAGE_SIZE);
+
+	err = xenbus_alloc_evtchn(dev, &info->evtchn);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "xenbus_alloc_evtchn");
+		goto fail;
+	}
+
+	err = bind_evtchn_to_irq_lateeoi(info->evtchn);
+	if (err <= 0) {
+		xenbus_dev_fatal(dev, err, "bind_evtchn_to_irq_lateeoi");
+		goto fail;
+	}
+
+	info->irq = err;
+
+	err = request_threaded_irq(info->irq, NULL, xenhcd_int,
+				   IRQF_ONESHOT, "xenhcd", info);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "request_threaded_irq");
+		goto free_irq;
+	}
+
+	return 0;
+
+free_irq:
+	unbind_from_irqhandler(info->irq, info);
+fail:
+	xenhcd_destroy_rings(info);
+	return err;
+}
+
+static int xenhcd_talk_to_backend(struct xenbus_device *dev,
+				  struct xenhcd_info *info)
+{
+	const char *message;
+	struct xenbus_transaction xbt;
+	int err;
+
+	err = xenhcd_setup_rings(dev, info);
+	if (err)
+		return err;
+
+again:
+	err = xenbus_transaction_start(&xbt);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "starting transaction");
+		goto destroy_ring;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "urb-ring-ref", "%u",
+			    info->urb_ring_ref);
+	if (err) {
+		message = "writing urb-ring-ref";
+		goto abort_transaction;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "conn-ring-ref", "%u",
+			    info->conn_ring_ref);
+	if (err) {
+		message = "writing conn-ring-ref";
+		goto abort_transaction;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
+			    info->evtchn);
+	if (err) {
+		message = "writing event-channel";
+		goto abort_transaction;
+	}
+
+	err = xenbus_transaction_end(xbt, 0);
+	if (err) {
+		if (err == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, err, "completing transaction");
+		goto destroy_ring;
+	}
+
+	return 0;
+
+abort_transaction:
+	xenbus_transaction_end(xbt, 1);
+	xenbus_dev_fatal(dev, err, "%s", message);
+
+destroy_ring:
+	xenhcd_destroy_rings(info);
+
+	return err;
+}
+
+static int xenhcd_connect(struct xenbus_device *dev)
+{
+	struct xenhcd_info *info = dev_get_drvdata(&dev->dev);
+	struct xenusb_conn_request *req;
+	int idx, err;
+	int notify;
+	char name[TASK_COMM_LEN];
+	struct usb_hcd *hcd;
+
+	hcd = xenhcd_info_to_hcd(info);
+	snprintf(name, TASK_COMM_LEN, "xenhcd.%d", hcd->self.busnum);
+
+	err = xenhcd_talk_to_backend(dev, info);
+	if (err)
+		return err;
+
+	/* prepare ring for hotplug notification */
+	for (idx = 0; idx < XENUSB_CONN_RING_SIZE; idx++) {
+		req = RING_GET_REQUEST(&info->conn_ring, idx);
+		req->id = idx;
+	}
+	info->conn_ring.req_prod_pvt = idx;
+
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->conn_ring, notify);
+	if (notify)
+		notify_remote_via_irq(info->irq);
+
+	return 0;
+}
+
+static void xenhcd_disconnect(struct xenbus_device *dev)
+{
+	struct xenhcd_info *info = dev_get_drvdata(&dev->dev);
+	struct usb_hcd *hcd = xenhcd_info_to_hcd(info);
+
+	usb_remove_hcd(hcd);
+	xenbus_frontend_closed(dev);
+}
+
+static void xenhcd_watchdog(struct timer_list *timer)
+{
+	struct xenhcd_info *info = timer_container_of(info, timer, watchdog);
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->lock, flags);
+	if (likely(HC_IS_RUNNING(xenhcd_info_to_hcd(info)->state))) {
+		xenhcd_timer_action_done(info, TIMER_RING_WATCHDOG);
+		xenhcd_giveback_unlinked_urbs(info);
+		xenhcd_kick_pending_urbs(info);
+	}
+	spin_unlock_irqrestore(&info->lock, flags);
+}
+
+/*
+ * one-time HC init
+ */
+static int xenhcd_setup(struct usb_hcd *hcd)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+
+	spin_lock_init(&info->lock);
+	INIT_LIST_HEAD(&info->pending_submit_list);
+	INIT_LIST_HEAD(&info->pending_unlink_list);
+	INIT_LIST_HEAD(&info->in_progress_list);
+	INIT_LIST_HEAD(&info->giveback_waiting_list);
+	timer_setup(&info->watchdog, xenhcd_watchdog, 0);
+
+	hcd->has_tt = (hcd->driver->flags & HCD_MASK) != HCD_USB11;
+
+	return 0;
+}
+
+/*
+ * start HC running
+ */
+static int xenhcd_run(struct usb_hcd *hcd)
+{
+	hcd->uses_new_polling = 1;
+	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
+	hcd->state = HC_STATE_RUNNING;
+	return 0;
+}
+
+/*
+ * stop running HC
+ */
+static void xenhcd_stop(struct usb_hcd *hcd)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+
+	timer_delete_sync(&info->watchdog);
+	spin_lock_irq(&info->lock);
+	/* cancel all urbs */
+	hcd->state = HC_STATE_HALT;
+	xenhcd_cancel_all_enqueued_urbs(info);
+	xenhcd_giveback_unlinked_urbs(info);
+	spin_unlock_irq(&info->lock);
+}
+
+/*
+ * called as .urb_enqueue()
+ * non-error returns are promise to giveback the urb later
+ */
+static int xenhcd_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
+			      gfp_t mem_flags)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+	struct urb_priv *urbp;
+	unsigned long flags;
+	int ret;
+
+	if (unlikely(info->error))
+		return -ESHUTDOWN;
+
+	urbp = kmem_cache_zalloc(xenhcd_urbp_cachep, mem_flags);
+	if (!urbp)
+		return -ENOMEM;
+
+	spin_lock_irqsave(&info->lock, flags);
+
+	urbp->urb = urb;
+	urb->hcpriv = urbp;
+	urbp->req_id = ~0;
+	urbp->unlink_req_id = ~0;
+	INIT_LIST_HEAD(&urbp->list);
+	urbp->status = 1;
+	urb->unlinked = false;
+
+	ret = xenhcd_submit_urb(info, urbp);
+
+	if (ret)
+		xenhcd_free_urb_priv(urbp);
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return ret;
+}
+
+/*
+ * called as .urb_dequeue()
+ */
+static int xenhcd_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
+{
+	struct xenhcd_info *info = xenhcd_hcd_to_info(hcd);
+	struct urb_priv *urbp;
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&info->lock, flags);
+
+	urbp = urb->hcpriv;
+	if (urbp) {
+		urbp->status = status;
+		ret = xenhcd_unlink_urb(info, urbp);
+	}
+
+	spin_unlock_irqrestore(&info->lock, flags);
+
+	return ret;
+}
+
+/*
+ * called from usb_get_current_frame_number(),
+ * but, almost all drivers not use such function.
+ */
+static int xenhcd_get_frame(struct usb_hcd *hcd)
+{
+	/* it means error, but probably no problem :-) */
+	return 0;
+}
+
+static const struct hc_driver xenhcd_usb20_hc_driver = {
+	.description = "xen-hcd",
+	.product_desc = "Xen USB2.0 Virtual Host Controller",
+	.hcd_priv_size = sizeof(struct xenhcd_info),
+	.flags = HCD_USB2,
+
+	/* basic HC lifecycle operations */
+	.reset = xenhcd_setup,
+	.start = xenhcd_run,
+	.stop = xenhcd_stop,
+
+	/* managing urb I/O */
+	.urb_enqueue = xenhcd_urb_enqueue,
+	.urb_dequeue = xenhcd_urb_dequeue,
+	.get_frame_number = xenhcd_get_frame,
+
+	/* root hub operations */
+	.hub_status_data = xenhcd_hub_status_data,
+	.hub_control = xenhcd_hub_control,
+#ifdef CONFIG_PM
+	.bus_suspend = xenhcd_bus_suspend,
+	.bus_resume = xenhcd_bus_resume,
+#endif
+};
+
+static const struct hc_driver xenhcd_usb11_hc_driver = {
+	.description = "xen-hcd",
+	.product_desc = "Xen USB1.1 Virtual Host Controller",
+	.hcd_priv_size = sizeof(struct xenhcd_info),
+	.flags = HCD_USB11,
+
+	/* basic HC lifecycle operations */
+	.reset = xenhcd_setup,
+	.start = xenhcd_run,
+	.stop = xenhcd_stop,
+
+	/* managing urb I/O */
+	.urb_enqueue = xenhcd_urb_enqueue,
+	.urb_dequeue = xenhcd_urb_dequeue,
+	.get_frame_number = xenhcd_get_frame,
+
+	/* root hub operations */
+	.hub_status_data = xenhcd_hub_status_data,
+	.hub_control = xenhcd_hub_control,
+#ifdef CONFIG_PM
+	.bus_suspend = xenhcd_bus_suspend,
+	.bus_resume = xenhcd_bus_resume,
+#endif
+};
+
+static struct usb_hcd *xenhcd_create_hcd(struct xenbus_device *dev)
+{
+	int i;
+	int err = 0;
+	int num_ports;
+	int usb_ver;
+	struct usb_hcd *hcd = NULL;
+	struct xenhcd_info *info;
+
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "num-ports", "%d",
+			   &num_ports);
+	if (err != 1) {
+		xenbus_dev_fatal(dev, err, "reading num-ports");
+		return ERR_PTR(-EINVAL);
+	}
+	if (num_ports < 1 || num_ports > XENUSB_MAX_PORTNR) {
+		xenbus_dev_fatal(dev, err, "invalid num-ports");
+		return ERR_PTR(-EINVAL);
+	}
+
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "usb-ver", "%d", &usb_ver);
+	if (err != 1) {
+		xenbus_dev_fatal(dev, err, "reading usb-ver");
+		return ERR_PTR(-EINVAL);
+	}
+	switch (usb_ver) {
+	case XENUSB_VER_USB11:
+		hcd = usb_create_hcd(&xenhcd_usb11_hc_driver, &dev->dev,
+				     dev_name(&dev->dev));
+		break;
+	case XENUSB_VER_USB20:
+		hcd = usb_create_hcd(&xenhcd_usb20_hc_driver, &dev->dev,
+				     dev_name(&dev->dev));
+		break;
+	default:
+		xenbus_dev_fatal(dev, err, "invalid usb-ver");
+		return ERR_PTR(-EINVAL);
+	}
+	if (!hcd) {
+		xenbus_dev_fatal(dev, err,
+				 "fail to allocate USB host controller");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	info = xenhcd_hcd_to_info(hcd);
+	info->xbdev = dev;
+	info->rh_numports = num_ports;
+
+	for (i = 0; i < XENUSB_URB_RING_SIZE; i++) {
+		info->shadow[i].req.id = i + 1;
+		info->shadow[i].urb = NULL;
+		info->shadow[i].in_flight = false;
+	}
+	info->shadow[XENUSB_URB_RING_SIZE - 1].req.id = 0x0fff;
+
+	return hcd;
+}
+
+static void xenhcd_backend_changed(struct xenbus_device *dev,
+				   enum xenbus_state backend_state)
+{
+	switch (backend_state) {
+	case XenbusStateInitialising:
+	case XenbusStateReconfiguring:
+	case XenbusStateReconfigured:
+	case XenbusStateUnknown:
+		break;
+
+	case XenbusStateInitWait:
+	case XenbusStateInitialised:
+	case XenbusStateConnected:
+		if (dev->state != XenbusStateInitialising)
+			break;
+		if (!xenhcd_connect(dev))
+			xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		fallthrough;	/* Missed the backend's Closing state. */
+	case XenbusStateClosing:
+		xenhcd_disconnect(dev);
+		break;
+
+	default:
+		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+				 backend_state);
+		break;
+	}
+}
+
+static void xenhcd_remove(struct xenbus_device *dev)
+{
+	struct xenhcd_info *info = dev_get_drvdata(&dev->dev);
+	struct usb_hcd *hcd = xenhcd_info_to_hcd(info);
+
+	xenhcd_destroy_rings(info);
+	usb_put_hcd(hcd);
+}
+
+static int xenhcd_probe(struct xenbus_device *dev,
+			const struct xenbus_device_id *id)
+{
+	int err;
+	struct usb_hcd *hcd;
+	struct xenhcd_info *info;
+
+	if (usb_disabled())
+		return -ENODEV;
+
+	hcd = xenhcd_create_hcd(dev);
+	if (IS_ERR(hcd)) {
+		err = PTR_ERR(hcd);
+		xenbus_dev_fatal(dev, err,
+				 "fail to create usb host controller");
+		return err;
+	}
+
+	info = xenhcd_hcd_to_info(hcd);
+	dev_set_drvdata(&dev->dev, info);
+
+	err = usb_add_hcd(hcd, 0, 0);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "fail to add USB host controller");
+		usb_put_hcd(hcd);
+		dev_set_drvdata(&dev->dev, NULL);
+	}
+
+	return err;
+}
+
+static const struct xenbus_device_id xenhcd_ids[] = {
+	{ "vusb" },
+	{ "" },
+};
+
+static struct xenbus_driver xenhcd_driver = {
+	.ids			= xenhcd_ids,
+	.probe			= xenhcd_probe,
+	.otherend_changed	= xenhcd_backend_changed,
+	.remove			= xenhcd_remove,
+};
+
+static int __init xenhcd_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	xenhcd_urbp_cachep = kmem_cache_create("xenhcd_urb_priv",
+					sizeof(struct urb_priv), 0, 0, NULL);
+	if (!xenhcd_urbp_cachep) {
+		pr_err("xenhcd failed to create kmem cache\n");
+		return -ENOMEM;
+	}
+
+	return xenbus_register_frontend(&xenhcd_driver);
+}
+module_init(xenhcd_init);
+
+static void __exit xenhcd_exit(void)
+{
+	kmem_cache_destroy(xenhcd_urbp_cachep);
+	xenbus_unregister_driver(&xenhcd_driver);
+}
+module_exit(xenhcd_exit);
+
+MODULE_ALIAS("xen:vusb");
+MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
+MODULE_DESCRIPTION("Xen USB Virtual Host Controller driver (xen-hcd)");
+MODULE_LICENSE("Dual BSD/GPL");